This invention relates to a reinforcing combination or assembly for use with plate metal such as automobile door panels, and a reinforcement configuration resulting from such a reinforcing assembly attached to plate metal.
It is well known in the automobile art that great efforts have recently been made to reduce the weight of vehicle bodies for the purpose of improving fuel consumption. Steel plates from which vehicle bodies are fabricated are then required to be as thin as possible. With such a reduction in thickness of body-forming steel plates, there have newly arisen problems that they are readily dented under local external forces and that vibration is increased to generate more noise.
One prior art method for solving such problems is to attach a thermosetting sheet of epoxy or butyl type to the inner surface of a body panel followed by heat curing of the sheet. The use of thermosetting sheets of epoxy and butyl types for reinforcement is successful in increasing the rigidity of panels at the sacrifice of the production cost of automobiles because these thermosetting sheets are relatively expensive. Further, automobile body panels for use as automobile bodies are not required to have high tensile rigidity, dent resistance and vibration damping properties over the entire area, but are required to have different properties for different areas. If a thermosetting sheet is attached to the entire area of the panel, rigidity is locally increased to an unnecessarily high level or conversely, certain properties are locally lower than the required level. As a result, expenditure is lost in vain to raise manufacturing cost. In addition, the body weight is correspondingly increased against the principal purpose of reducing the thickness of body-forming steel plates. The above-mentioned conventional reinforcing material in the form of an adhesive sheet, once attached to a body panel, is difficult to separate from the panel. Even when separable, the reinforcing material is imperatively broken in separating it from the panel. The conventional reinforcing material must be carefully and precisely attached to the panel so that attaching operation is time consuming and requires a skill. Furthermore, the conventional thermosetting sheets tend to cause the panel to be strained or warped because of their increased percentage shrinkage and shrinkage stress upon curing.
In order to overcome the problems associated with the shrinkage of such reinforcing sheets, Japanese Patent Application Kokai No. SHO 52-1507 proposes to use the reinforcing sheet in segments. Attaching a number of reinforcing sheet segments is time consuming and cumbersome and is not acceptable in practice.
A further method for reinforcing panels is disclosed in Japanese Patent Application Kokai No. SHO 57-151316 in which a resinous material containing a foaming agent is completely covered with a thermosetting resin and they are heat cured to form a tunnel-like reinforcing rib. The reinforcing material disclosed in this patent application is successful in weight reduction due to the use of the foaming agent and in avoiding the occurrence of strain and warpage, but it cannot fully damp vibration.